This project will investigate the biological basis of early visual information processing dysfunction in patients with schizophrenia. The visual backward masking (VBM) paradigm has revealed characteristic visual processing deficits in patients with schizophrenia. In schizophrenia, visual targets require longer processing time to "escape" the effects of a subsequent mask stimulus, indicating dysfunction at a basic level of visual processing. This deficit correlates strongly with the severity of persistent negative symptoms in medicated patients. Human visual processing is conducted through parallel Parvocellular (P) and Magnocellular (M) pathways. Visual processing deficits in schizophrenia may, therefore, reflect isolated dysfunction in either the M or P system, or a dysfunctional interaction of these systems. We have formed an IRPG group to define neural mechanisms of early visual processing deficits in schizophrenia. There are two projects with interlocking roles. Experiments in humans (this application) will use both behavioral and visual evoked potential (VEP) measures to evaluate the integrity of the M and P pathways in schizophrenia and to define the isolated or interactive roles of the M and P systems in VBM. Experiments in monkeys (the accompanying IRPG application) will pursue direct brain electrical recordings in behaving monkeys in order to evaluate and refine he P- and M-specificity of the stimuli used in the human studies and to describe neural mechanisms of VBM at the level of specific cortical regions, neuronal populations, and cellular processes. Shared resource cores will support stimulus development and data analysis. The stimulus development shared resource will permit development of specific M and P stimuli and support collaborators with expertise in visual psychophysiology, electrophysiology and etiopathology. The data analysis shared resource will permit rapid and flexible application of closely coordinated analysis strategies to data from both species and support a collaborator with unique expertise in integrated human/monkey studies and in the proposed analyses.